The invention relates to a wheelchair modified for propelling by a pivoting action of the user""s lower legs about the knee joints.
Wheelchairs are commonly in use by people having weakness in their legs or balance problems. The present invention is concerned with providing a wheelchair which the user can propel by pivoting his lower legs about the knee joints, to thereby exercise his leg muscles.
The conventional wheelchair comprises:
a frame supporting a seat;
a pair of free-wheeling large drive wheels rotatably mounted to the rear end of the frame;
one or more free-wheeling, pivoting caster wheels mounted to the front end of the frame;
a footrest extending down from the front of the frame, for supporting the lower legs; and
circular push rims projecting outwardly from the rear wheels.
The user grasps the push rims with his hands and propels the wheelchair forward or backwards using his arms and upper body. Pushing of the left and right push rims at different intensities or in different directions allows the chair to gradually turn or to xe2x80x9cpivot on the spotxe2x80x9d.
Propelling the wheelchair with the hands, arms and upper body can lead to overuse injuries due to the somewhat unnatural movements performed in driving the push rims. In addition, the lower legs get no exercise and the leg muscles can atrophy. As a result, bones in the legs may become weaker and this can lead to fractures.
A number of proposals have been made in the prior art with respect to modifying wheelchairs to address these problems.
One approach involves providing levers to be pushed or pulled by the arms to power the wheels. The two-direction oscillation of the push and pull strokes is converted to rotational motion through a lever system and then converted to a unidirectional rotational motion through the use of a ratchet and pawl or one-way clutch system, to power one or both of the rear wheels. However this approach still relies on the upper body strength of the user to power the movement of the chair. U.S. Pat. No. 3,994,509, issued to Schaeffer, is an example.
Other prior art devices have focussed on using the legs to power the chair. More particularly, U.S. Pat. No. 4,766,772, issued to Tsuchie, disclosed a pedaling assembly for rotating the wheels of a wheelchair. U.S. Pat. Nos. 4,421,336 issued to Petrofsky et al and 4,523,769, issued to Glaser et al, disclose an assembly utilizing back and forth sliding of the feet to propel the chair.
U.S. Pat. No. 4,486,048, issued to Mayer, discloses a pivoting footrest. U.S. Pat. No. 5,033,793, issued to Quintile, shows a telescoping footrest. U.S. Pat. No. 4,586,723, issued to Nabinger, shows a steering caster assembly.
It is an objective of the invention to modify a wheelchair so that pivoting of the user""s lower legs about the knee joints, by extension and flexion of the knees, is used to propel the wheelchair.
In a preferred embodiment, the invention comprises:
a wheelchair having a frame, seat and front and rear wheels;
a horizontal shaft rotatably mounted to the front end of the frame at an elevation below that of the top surface of the seat;
a telescoping input lever pivotally connected at its upper end with the shaft at an elevation below the top surface of the seat and having a foot rest at its lower end, to which the user""s feet are secured, whereby extension and flexion of the knees induces oscillating rotation of the shaft. The telescoping nature of the lever enables the axis of the knees to remain stationary, even though the pivot point of the lever is below that of the knee joints;
means for controlling the extent of telescoping of the input lever so as to ensure that the foot rest supports or bears at least part of the load of the legs and the lever;
drive assembly means, engaging the shaft with a rear wheel of the wheelchair, for converting the oscillating motion of the shaft into forward rotational motion and transmitting it to the wheel to drive it;
means, controllable by the user, for selectively engaging or disengaging the drive assembly means so that the wheels can freely rotate; and
means, manually controllable by the user, for steering at least one front caster wheel to control the direction of the wheelchair""s forward movement.
In one embodiment, there is provided a wheelchair having a frame pivotally connected with a telescoping input lever, that can be oscillated by extension and flexion of at least one of the user""s knees. A drive assembly connects the input lever with a wheel of the wheelchair, for converting the oscillating motion of the lever into forward rotational motion and transmitting it to the wheel to drive it.
To the best of my knowledge, it is novel to propel a wheeled frame using a lower leg, pivoting at the knee, to actuate a pivoting input lever secured to the leg to thereby produce an oscillating pivoting motion that is then converted to a forward rotational motion which is transmitted to a drive wheel to move the assembly.